Ultrawideband characteristics of fractal dipole antennas integrated on Si for ULSI wireless interconnects

Ultrawideband characteristics of Sierpinski carpet fractal antennas fabricated on silicon substrates with the resistivities of 2290, 79.6, and 10 /spl Omega//spl middot/cm were investigated. The return losses lower than -10 dB and high transmission gains of approximately -14 dB were obtained for the antennas with 10-mm distance on the Si substrate with the resistivity of 2290 /spl Omega//spl middot/cm in the frequency range from 18 to 26.5 GHz. Gaussian monocycle pulses with 70 ps pulsewidth were transmitted in the Si substrates successfully and the corresponding voltage gains were -23, -26, and -39 dB for the Si resistivities of 2290, 79.6, and 10 /spl Omega//spl middot/cm, respectively.     

High transmission gain inverted-F antenna on low-resistivity Si for wireless interconnect

Inverted-F antennas of 2-mm axial length are designed and fabricated on a low-resistivity silicon substrate (10 /spl Omega//spl middot/cm) using a post back-end-of-line process. For the first time, their performances are measured up to 110 GHz for wireless interconnects. Results show that a sharp resonance can be seen at 61 GHz for the antenna, and a high transmission gain of -46.3 dB at 61 GHz is achieved from the pair of inverted-F antennas at a separation of 10 mm on a standard 10 /spl Omega//spl middot/cm silicon wafer of 750-/spl mu/m thickness.     

Integrated antennas on silicon substrates for communication over free space

This letter reports the feasibility of using 2-mm-long on-chip antennas for communication over free space. Integration of antennas into radio frequency integrated circuits (RFICs) eliminates external transmission line connections and sophisticated packaging, which should lower the cost of wireless systems operating above 10 GHz. Mobile microwave probe stands have been developed for measurements at varying antenna pair separations. Antenna-pair gains for 2-mm-long integrated zigzag dipole antennas fabricated on 20-/spl Omega/-cm silicon substrates have been characterized near 24 GHz for separations up to 15 m. The antenna-pair gains show R/sup -2/ dependence up to /spl sim/4-5 m. The antennas were found to be sufficient for use up to 5 m and possibly larger separations.     

A low-voltage 40-GHz complementary VCO with 15% frequency tuning range in SOI CMOS technology

The design of a low-voltage 40-GHz complementary voltage-controlled oscillator (VCO) with 15% frequency tuning range fabricated in 0.13-/spl mu/m partially depleted silicon-on-insulator (SOI) CMOS technology is reported. Technological advantages of SOI over bulk CMOS are demonstrated, and the accumulation MOS (AMOS) varactor limitations on frequency tuning range are addressed. At 1.5-V supply, the VCO core and each output buffer consumes 11.25 mW and 3 mW of power, respectively. The measured phase noise at 40-GHz is -109.73 dBc/Hz at 4-MHz offset from the carrier, and the output power is -8 dBm. VCO performance using high resistivity substrate (/spl sim/300-/spl Omega//spl middot/cm) has the same frequency tuning range but 2 dB better phase noise compared with using low resistivity substrate (10 /spl Omega//spl middot/cm). The VCO occupies a chip area of only 100 /spl mu/m by 100 /spl mu/m (excluding pads).     

12 W/mm AlGaN-GaN HFETs on silicon substrates

Al/sub 0.26/Ga/sub 0.74/N-GaN heterojunction field-effect transistors were grown by metal-organic chemical vapor deposition on high-resistivity 100-mm Si (111) substrates. Van der Pauw sheet resistance of the two-dimensional electron gas was 300 /spl Omega//square with a standard deviation of 10 /spl Omega//square. Maximum drain current density of /spl sim/1 A/mm was achieved with a three-terminal breakdown voltage of /spl sim/200 V. The cutoff frequency and maximum frequency of oscillation were 18 and 31 GHz, respectively, for 0.7-/spl mu/m gate-length devices. When biased at 50 V, a 2.14-GHz continuous wave power density of 12 W/mm was achieved with associated large-signal gain of 15.3 dB and a power-added efficiency of 52.7%. This is the highest power density ever reported from a GaN-based device grown on a silicon substrate, and is competitive with the best results obtained from conventional device designs on any substrate.     

Attenuation mechanisms of aluminum millimeter-wave coplanar waveguides on silicon

The loss mechanisms of silicon coplanar waveguides (CPW) with aluminum metallization are investigated up to 40 GHz. Three main parts contribute to the attenuation of coplanar waveguides (CPWs): the frequency-dependent conductor losses of the metallization, frequency-independent substrate losses, and the specifically investigated bias-dependent interface losses caused by free charges at the Si-SiO/sub 2/ interface. The minimum losses found in 50-/spl Omega/ CPWs with 45-/spl mu/m signal line width were 0.19 db/mm at 10 GHz and 0.33 dB/mm at 40 GHz. High-purity silicon from a float zone (FZ) process was used as substrate. Substrates with lower purity from a Czochralski (CZ) process (resistivity 50-100 /spl Omega/cm) resulted in somewhat higher (0.2-0.3 dB/mm) losses for the same CPW geometry.     

5.8-GHz circularly polarized rectifying antenna for wireless microwave power transmission

This paper reports a new circularly polarized (CP) high-gain high-efficiency rectifying antenna (rectenna). The CP rectenna can be rotated and still maintain a constant dc output voltage. The high-gain antenna has an advantage of reducing the total number of rectenna elements to cover a fixed area. The rectenna is etched on Rogers Duroid 5870 substrate with /spl epsi//sub r/=2.33 and 10 mil thickness. A high-gain dual-rhombic-loop antenna and a reflecting plane are used to achieve a CP antenna gain of 10.7 dB and a 2:1 voltage standing-wave ratio bandwidth of 10%. The rectenna's pattern has an elliptical cross section with orthogonal beamwidths of 40/spl deg/ and 60/spl deg/. The rectenna circuit has a coplanar stripline band-reject filter that suppresses the re-radiated harmonics by 20 dB. A highly efficient Schottky diode is used for RF-to-dc conversion with an efficiency of approximately 80% for an input power level of 100 mW and a load resistance of 250 /spl Omega/.     

Wafer-level packaging technology for high-Q on-chip inductors and transmission lines

In the current trend toward portable applications, high-Q integrated inductors have gained considerable importance. Hence, much effort has been spent to increase the performance of on-chip Si inductors. In this paper, wafer-level packaging (WLP) techniques have been used to integrate state-of-the-art high-Q on-chip inductors on top of a five-levels-of-metal Cu damascene back-end of line (BEOL) silicon process using 20-/spl Omega//spl middot/cm Si wafers. The inductors are realized above passivation using thick post-processed low-K dielectric benzocyclobutene (BCB) and Cu layers. For a BCB-Cu thickness of 16 /spl mu/m/10 /spl mu/m, a peak single-ended Q factor of 38 at 4.7 GHz has been measured for a 1-nH inductor with a resonance frequency of 28 GHz. Removing substrate contacts slightly increases the performance, though a more significant improvement has been obtained by combining post-processed passives with patterned ground shields: for a 2.3-nH above integrated-circuit (above-IC) inductor, a 115% increase in Q/sub BW//sup max/ (37.5 versus 17.5) and a 192% increase in resonance frequency (F/sub res/: 12 GHz versus 5 GHz) have been obtained as compared to the equivalent BEOL realization with a patterned ground shield. Next to inductors, high-quality on-chip transmission lines may be realized in the WLP layers. Losses below -0.2 dB/mm at 25 GHz have been measured for 50-/spl Omega/ post-processed coplanar-waveguide lines, above-IC thin-film microstrip lines have measured losses below -0.12 dB/mm at 25 GHz.     

Sub-500/spl deg/C solid-phase epitaxy of ultra-abrupt p/sup +/-silicon elevated contacts and diodes

A well-controlled low-temperature process, demonstrated from 350/spl deg/C to 500/spl deg/C, has been developed for epitaxially growing elevated contacts and near-ideal diode junctions of Al-doped Si in contact windows to the Si substrate. A physical-vapor-deposited (PVD) amorphous silicon layer is converted to monocrystalline silicon selectively in the contact windows by using a PVD aluminum layer as a transport medium. This is a solid-phase-epitaxy (SPE) process by which the grown Si is Al-doped to at least 10/sup 18/ cm/sup -3/. Contact resistivity below 10/sup -7/ /spl Omega//spl middot/cm/sup 2/ is achieved to both p/sup -/ and p/sup +/ bulk-silicon regions. The elevated contacts have also been employed to fabricate p/sup +/-n diodes and p/sup +/-n-p bipolar transistors, the electrical characterization of which indicates a practically defect-free epitaxy at the interface.     

Multifunctional microstrip transmission lines integrated with defected ground structure for RF front-end application

This paper presents multifunctional microstrip transmission lines for designing a high port-isolation dual-frequency orthogonally polarized rectangular patch antenna and the antenna-integrated power amplifier. The proposed lines were realized through the integration of defected ground structures (DGSs) with conventional microstrip lines. A spiral-shaped DGS-integrated microstrip line enhances the port isolation of the antenna, while feeding the 2.0-GHz excitation to the antenna and filtering out the 2.5-GHz receiving signal from the other port. High-order harmonic signal suppression of the power amplifier at the 2.5-GHz port was accomplished by the dumbbell-shaped DGS, thereby improving the efficiency of the amplifier. Measurements show an improvement of 20 dB in port isolation and 3% in power-added efficiency relative to an identical RF front-end, but integrated with a conventional patch antenna. An image impedance of the DGS-integrated microstrip lines can be controlled by the integrated DGS geometries. Relatively high-impedances lines, i.e., 150 and 100 /spl Omega/, are effectively implemented using microstrip lines with 75- and 50-/spl Omega/ linewidths by incorporating the spiral- and dumbbell-shaped DGSs, respectively.     

Printed compact dual band antenna for 2.4 and 5 GHz ISM band applications

A printed compact dipole antenna for dual ISM band (2.44 and 5 GHz) is presented. The proposed antenna fed by using a 50 /spl Omega/ coaxial line occupies a volume of 15/spl times/40/spl times/1 mm/sup 3/ (FR-4, permittivity 4.6). The impedance bandwidth for 10 dB return loss is about 400 MHz (from 2170 to 2570 MHz) at 2.4 GHz band and over 2300 MHz (from 4690 to beyond 7000 MHz) at 5 GHz band. The measured radiation gains range from 1.20 to 1.41 dBi at 2.4 GHz band and from 2.25 to 3.44 dBi at 5 GHz band, respectively.     

Single aperture monopulse horn antenna

This paper describes the design and performance of a conical Potter horn antenna which can generate sum or difference far field patterns suitable for monopulse tracking applications. The antenna consists of a horn antenna fed with a metal post loaded polarizer which is energised by suitably phased 50-/spl Omega/ matched coaxial probes. The prototype demonstrator designed here operates in the frequency range 8-8.6GHz with sum and difference patterns obtained by using a very simple phasing circuit. At 8.5GHz, the gain of the sum pattern is 18.6dB and the in the difference pattern is 26dB at boresight.     

High-performance microwave coplanar bandpass and bandstop filters on Si substrates

High-performance bandpass and bandstop microwave coplanar filters, which operate from 22 to 91 GHz, have been fabricated on Si substrates. This was achieved using an optimized proton implantation process that converts the standard low-resistivity (/spl sim/10 /spl Omega//spl middot/cm) Si to a semi-insulating state. The bandpass filters consist of coupled lines to form a series resonator, while the bandstop filter was designed in a double-folded short-end stub structure. For the bandpass filters at 40 and 91 GHz, low insertion loss was measured, close to electromagnetic simulation values. We also fabricated excellent bandstop filters with very low transmission loss of /spl sim/1 dB and deep band rejection at both 22 and 50 GHz. The good filter performance was confirmed by the higher substrate impedance to ground, which was extracted from the well-matched S-parameter equivalent-circuit data.     

Characterization of copper germanide as contact metal for advanced MOSFETs

The material and electrical characteristics of /spl epsiv/-Cu/sub 3/Ge as a contact metal were investigated. The samples were prepared by direct copper deposition on germanium wafers, followed by rapid thermal annealing. The /spl epsiv/-Cu/sub 3/Ge formed at 400 /spl deg/C has a resistivity of 6.8 /spl mu//spl Omega//spl middot/cm, which is lower than typical silicides for silicon CMOS. Cross-sectional transmission electron microscopy showed smooth germanide/germanium interface, with a series of nanovoids aligning close to the top surface. These voids are believed to be the results of Kirkendall effect arising from the different diffusion fluxes of copper and germanium. The specific contact resistivity of Cu/sub 3/Ge, obtained from four-terminal Kelvin structures, was found to be as low as 8/spl times/10/sup -8/ /spl Omega//spl middot/cm/sup 2/ for p-type germanium substrate. This low resistivity makes Cu/sub 3/Ge a promising candidate for future contact materials.     

Optical receiver IC for CD/DVD/blue-laser application

In this paper, an optoelectronic receiver IC for CD, DVD, and Blue-Laser optical data storage applications is presented. The IC was developed in a 0.5-/spl mu/m BiCMOS technology with integrated PIN photodiodes. It includes a new architecture of high-speed and low-noise variable gain transimpedance amplifiers witch current preamplifier input. The amplifier transimpedance gain is programmable over a gain range of 130 /spl Omega/ to 270 k/spl Omega/ by a serial interface. The amplifier small-signal bandwidth is 260 MHz for the highest gain, which gives a gain-bandwidth product of 70 THz/spl Omega/ and a sensitivity improvement by a factor of 2 compared to published OEICs. The amplifiers support a special write/clip mode which realizes a nonlinear gain reduction for high input signals. The output voltage buffers are 130-/spl Omega/ impedance matched for optimized data transmission over a flex cable. The impedance is generated by active-impedance synthesis to increase the output dynamic range.     

Nonalloyed ohmic contacts in AlGaN/GaN HEMTs by ion implantation with reduced activation annealing temperature

This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose of 1/spl times/10/sup 16/ cm/sup -2/ and were activated at /spl sim/1260/spl deg/C in a metal-organic chemical vapor deposition system in ammonia and nitrogen at atmospheric pressure. Nonalloyed ohmic contacts to ion-implanted devices showed a contact resistance of 0.96 /spl Omega//spl middot/mm to the channel. An output power density of 5 W/mm was measured at 4 GHz, with 58% power-added efficiency and a gain of 11.7 dB at a drain bias of 30 V.     

A new Millimeter-wave printed dipole phased array antenna using microstrip-fed coplanar stripline tee junctions

A new millimeter-wave printed twin dipole phased array antenna is developed at Ka band using a new microstrip-fed CPS tee junction, which does not require any bonding wires, air bridges, or via holes. The phased array used a piezoelectric transducer (PET) controlled tunable multitransmission line phase shifter to accomplish a progressive phase shift. A progressive phase shift of 88.8/spl deg/ is achieved with the 5 mm of perturber length when the PET has full deflection. Measured return loss of the twin dipole antenna is better than 10 dB from 29.5 to 30.35 GHz. Measured return loss of better than 15 dB is achieved from 30 to 31.5 GHz for a 1/spl times/8 phased array. The phased array antenna has a measured antenna gain of 14.4 dBi with 42/spl deg/ beam scanning and has more than 11 dB side lobe suppression across the scan.     

Low noise RF MOSFETs on flexible plastic substrates

We report a low minimum noise figure (NF/sub min/) of 1.1 dB and high associated gain (12 dB at 10 GHz) for 16 gate-finger 0.18-/spl mu/m RF MOSFETs, after thinning down the Si substrate to 30 /spl mu/m and mounting it on plastic. The device performance was improved by flexing the substrate to create stress, which produced a 25% enhancement of the saturation drain current and lowered NF/sub min/ to 0.92 dB at 10 GHz. These excellent results for mechanically strained RF MOSFETs on plastic compare well with 0.13-/spl mu/m node (L/sub g/=80 nm) devices.     

High isolation dual-polarized patch antenna using integrated defected ground structure

This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2 and 2.5 GHz. Image impedance of a microstrip line with DGS is controlled by the DGS geometry without modifying the dimension of the line. A 150 /spl Omega/ high impedance line is effectively implemented using a microstrip line with 75 /spl Omega/ line width by incorporating the DGS.     

A 700-GHz SIS antipodal finline mixer fed by a Pickett-Potter horn-reflector antenna

We report the successful operation of a superconductor-insulator-superconductor (SIS) finline mixer operating near the superconducting energy gap of Nb. The mixer employs a new type of Pickett-Potter horn-reflector (PPHR) antenna, which exhibits low sidelobes and low cross-polarization levels, and yet is easy to fabricate. The SIS tunnel junction and all of the integrated superconducting tuning circuits are fabricated from Nb using planar-circuit technology. The mixer employs an antipodal finline section, deposited on one side of a quartz substrate, which transforms the high impedance of the waveguide (/spl ap/300 /spl Omega/) to the low impedance of the microstrip line (/spl ap/20 /spl Omega/). The Nb/Al-oxide/Nb tunnel junction is fabricated at the same time as the finline circuit. In this paper, we describe the design and testing of the mixer, and pay particular attention to the electromagnetic design of the PPHR antenna. We investigate the noise temperature and gain of the mixer over 642-714 GHz, and analyze the experimental results using rigorous theories that were developed specifically for the purpose. Our investigation demonstrates that finline mixers have good performance both below and above the superconducting energy gap.